1. Field of Invention
This invention, the “Invention”, is a system for controlling the atmosphere within a container to inhibit the maturation of the produce contained therein by (1) preventing or limiting the formation of Ethylene, which is naturally produced by certain fruits and vegetables, (2) by scrubbing the atmosphere of any Ethylene that does form, (3) by exhausting the atmosphere of any residual Ethylene, (4) by limiting the amounts of Oxygen (O2) and Carbon Dioxide (CO2) to preset limits, and (5) by exhausting excess O2 and CO2. By eliminating, or greatly reducing Ethylene from the atmosphere surrounding the produce, it will arrive at destination in a state very near that in which it was harvested. Because maturation during shipping will be greatly reduced, fruit can be picked later, more developed; therefore, it should be more appealing to the consumer than fruit that is picked before its flavor has fully developed in order to accommodate the effects of maturation during shipping.
Ethylene gas (C2H4) is an odorless, colorless gas that exists in nature and occurs naturally as fruit and vegetables mature. Not easily detectable, it exists where produce is stored. In nature, the largest producers are plant and plant products (i.e., fruits, vegetables and floral products), which produce Ethylene within their tissues and release it into the surrounding atmosphere. Increased levels of Ethylene contained within a transport container and released by the produce itself serve as a stimulant after re-absorption to initiate the production of more Ethylene. The overall effect is to hasten ripening, aging and eventually spoilage.
The production of Ethylene, depends on the presence of Oxygen (O2) and Carbon Dioxide (CO2) in the atmosphere. By limiting these gases to very small amounts (O2<5%, CO2<15%) within a container, the production of Ethylene and its effect on the fruit is limited.
It is envisioned that this system will operate while the produce is being transported within a refrigerated container, utilizing the well-known benefits of refrigeration in sustaining produce quality by slowing its deterioration.
The Invention relies on flushing the atmosphere with Nitrogen as soon as possible after placing the produce in the transport container, and then maintaining the proper level of Nitrogen by allowing it to flow into the controlled area from a tank outside the cargo compartment of the container. The replacement of Oxygen by this gas creates an atmosphere that inhibits the formation of Ethylene. Filters then scrub from the controlled atmosphere any Ethylene that is formed. Finally, the system then periodically exhausts the atmosphere to remove any residual Ethylene and any excess O2 and CO2 above pre-determined optimum concentrations.
2. Comparison of the Invention with Prior Art
There have been previous attempts to establish a controlled atmosphere (CA) within which to store or transport perishable produce. These attempts have resulted in various systems that usually have approached the problem by utilizing a single method to improve or modify the atmosphere within a confined space.
One such system is known as the “NITROL” system (U.S. Pat. No. 3,239,360). This system relies on an ability to periodically purge the atmosphere with Nitrogen based on controls which respond to the Oxygen level within the environment of the shipping container. The only control therefore is based on Oxygen level and does not consider limiting the formation of Ethylene, or removing Ethylene from the atmosphere.
Another system, which has existed since approximately 1960, relies on the use of a seal inside of the container doors. The environment is then flushed with a premixed gas (trade name “TECTROL”). It differs from the NITROL system in that there is no monitoring or control of the environment during shipping other than in respect of temperature. Prior to the container being sealed, hydrated lime is placed within the container to absorb excessive amounts of Carbon Dioxide. The Carbon Dioxide and Oxygen control is not rigidly controlled to a pre-set level.